Argasidae

Argasidae, or soft ticks, is a family of parasitic arachnids in the order Ixodida. They are distinguished from the hard tick family Ixodidae by their soft, leathery body and the absence of a rigid dorsal scutum. The mouthparts are oriented downward and are not visible from above, and the capitulum is typically hidden ventrally. The family includes several genera, such as Argas, Ornithodoros, and Otobius.

Soft ticks feed quickly, usually taking only minutes to hours to obtain a blood meal, after which they detach and remain off-host for extended periods. They commonly inhabit the nesting sites, roosts, caves, or burrows of birds and mammals, sometimes within human structures where pest nests exist (e.g., pigeon roosts). They may feed on multiple hosts during their life cycle; many species show rapid, nocturnal feeding patterns.

Life cycle: eggs hatch into larvae with six legs, which molt into multiple nymphal instars (eight legs) before reaching adulthood. In many species the life cycle may be completed in a single year, but development is temperature dependent and can take longer in cooler climates. They can survive long dry spells and remain dormant between feeding events.

Medical and veterinary importance: Some Argasidae genera, especially Ornithodoros, are vectors of tick-borne relapsing fever caused by Borrelia species; others may transmit pathogens to livestock and wildlife. Pigeon ticks, Argas reflexus, can bite humans, causing dermatitis and allergic reactions in dwellings with seabird or pigeon roosts.

Distribution and diversity: The family is widespread in tropical, subtropical, and temperate regions, with numerous species adapted to nests, caves, and burrows. Major genera include Ornithodoros, Argas, and Otobius, the latter including Otobius megnini, the spinose ear tick, a common pest of livestock and companion animals.